I. Field of the Invention
This invention relates generally to equipment for disposing of used vehicle tires, and more particularly to a machine which reduces such tires to small size chips or particles that can later be used in the fabrication of various products or as a burnable fuel.
II. Discussion of the Prior Art
For many years, worn-out vehicle tires were commonly disposed of by burying same in landfills. Because vehicle tires are made from various synthetic rubber materials, they tend not to be biodegradable and, hence, will remain for many years buried in the earth. Because of environmental concerns and the premium being placed on space available for landfills, many such operations are refusing to accept worn-out vehicle tires for disposal. When stored above ground, they tend to become breeding grounds for mosquitoes and a potential fire hazard which can burn for weeks while emitting billowing clouds of black, soot-filled smoke.
Typical vehicle tires being made today are made up from a combination of steel, nylon cording and artificial rubber. The steel tends to be in the form of single or multi-filer strands which are woven into radial and circumferential belts and which are buried in the rubber. The artificial rubber is extremely rich in petroleum products and, when the tire is suitably pulverized, the resulting particulate can be burned as a fuel in an appropriately designed furnace for producing heat or steam but without creating environmentally destructive emissions.
In addition to being a burnable commodity, pulverized vehicle tires have found use in the fabrication of various products, such as roofing materials, additives to asphalt to be used for roadways and the like, etc.
Because of the nature of vehicle tires, they are quite difficult to reduce to a pulverized form. The steel belting and the steel bead surrounding the central opening become difficult to cut, especially when embedded in an elastomeric body.
The Granite U.S. Pat. No. 4,015,782 describes a machine for cutting up tire segments into small pieces or chips, but because of its design, it is not capable of dealing with steel belted radial tires. At the time that the application for the Granite patent was filed, steel belted radial tires were just coming on the scene and predominantly the tires which had worn out to the point where they were ready to be scrapped were of the solid rubber variety, such as shown in the drawings of that patent or, at most, they would only have glass belt construction.
When dealing with steel belted product, the teeth of the rotary cutting blades and the stationary cutting bars become worn after fairly short periods of use. As such, it becomes necessary to periodically resharpen the blades or go to the expense of replacing same. Because the apparatus shown in the Granite patent does not provide a means for precisely adjusting the tolerance or spacing between the stationary blades and the rotary cutting blades, it cannot accommodate the changes in blade dimension due to sharpening.
Another drawback of the device of the Granite patent is that there is no relief space provided in the rotary cutting blades into which cut pieces of tire can flow. Hence, the annular void or spacing between the parallel blades will tend to become packed with rubber fragments which becomes wedged therebetween, requiring frequent shut-down for maintenance purposes.
The Holman U.S. Pat. No. 3,931,935 describes yet another machine intended for reducing vehicle tires to small pieces or chunks. Here the device comprises a pair of parallel shafts each supporting a series of rotary knives or cutting disks which intermesh with one another. Devices built in accordance with the Holman patent tend to shred the tire by tearing it up rather than by slicing or cutting. Moreover, it is found that such a design does not allow the pieces to be reduced to a sufficiently small size which would allow them to be readily handled as a fuel.